The Amazon blurb was actually accurate, so I'm just quoting it here. Mare Barrow's world is divided by blood--those with common, Red blood serve the Silver- blooded elite, who are gifted with superhuman abilities. Mare is a Red, scraping by as a thief in a poor, rural village, until a twist of fate throws her in front of the Silver court. Before the king, princes, and all the nobles, she discovers she has an ability of her own.
To cover up this impossibility, the king forces her to play the role of a lost Silver princess and betroths her to one of his own sons. As Mare is drawn further into the Silver world, she risks everything and uses her new position to help the Scarlet Guard--a growing Red rebellion--even as her heart tugs her in an impossible direction. One wrong move can lead to her death, but in the dangerous game she plays, the only certainty is betrayal.
This is a debut novel, and I must say that I'm charmed by the crafting that Aveyard put into the main character, Mare. For all that Mare doesn't do much growing, she also is only in the story for perhaps a month or so, and a span of that time is glossed over due to her indoctrination period. And I have to acknowledge that she certainly changed during the book, even if that change wasn't actual "growth."
The two princes were basically stereotypical and trope-y, so it was Aveyard's details into that trope that made them interesting. The hurt in someone's eyes when they should have been happy or other observations of contradiction helped build depth even in the trope. The cast of secondary characters were mostly expected, and the details did get a smidge repetitive. The two trope straight-men (the loyal soldier and the mentor/teacher) were delightful, and I liked them the way I was supposed to.
From my memories and experience, I would say that Aveyard certainly has a good grasp on YA concerns, including sibling resentment/love and the perceived impact/received guilt that the heroine takes on due to people's choices or problems. Mare's major fluctuations among emotions are also not beyond credibility. And the creative use of all extremes, particularly the contrast between helpless outrage and absolute resignation to fate, was what I would expect from a teenager in such a precarious situation. The character crafting was skilled enough that I could even forgive the Hunger Games knockoff aspect of Mare always trying to protect a boy she doesn't actually love, and the competition between two romantic rivals. Kinda. Maybe.
The best part about the characters was that I was absolutely sure I had the plot trope pegged just from the character descriptions, but then Aveyard was so good at building the various twists that I started to doubt myself. Note the comment at the top - "The only certainty is betrayal." And oh, boy, howdy did she do a nice job with that. (And, by the way, my first guess was correct. Go me!)
There was an actually vaguely subtle (to me) part of the foreshadowing that made one of the twists in the climatic fight scene not entirely as implausible as it felt at first blush. I applaud Averyard for slipping that foreshadowing into the story so early that I'd forgotten about it every time it happened. Yes, I'm being deliberately vague, but I'll tell you in person if you ask.
Regarding the dystopian setup, I think that the world is kind of interesting at the hand-waving level, but the details were erratic. The setup of haves vs. have-nots is nothing new, just more extreme and widely ranged. (I've already read the first two in the Birthmarked series...) Aveyard also set up a lot of weird places where there was no detail, and then surprising detail. The "vehicle" vaguely describes like a car. Why not call it something more interesting, even if it's a made up name? They have jet airplanes but no motorcycles? They have blood-based ID cards but use paper vouchers for electricity? This war has been going on for more than 100 years because the guys with the superpowers don't fight and leave it all to the regular humans? (I'm not buyin' it.)
I picked this book up because it was a gift from my sister. I recommend this book to people who like a good palace intrigue and enjoy being almost a first-person shooter, literarily*. I don't recommend it to Ambyr, as the many and large world-building inconsistencies would drive her crazy.
*This is written in first person. This is written in present tense. It is my second most hated presentation format for a story that I've managed to read all the way through. I'm sure that person/tense choice is a part of the reason why I don't have much interest in going on with the story at the moment, though I know the sequel is coming out soon.